This invention relates to internal combustion engines, and, more particularly, to internal combustion engines having high surface to volume ratios such as rotary engines or short stroke reciprocating engines.
Prior art of possible relevance includes U.S. Pat. No. 3,440,929, issued Apr. 29, 1969 to Weissflog et al.
Present day rotary engines, and, to some extent, short stroke reciprocating engines, characteristically have a high surface to volume ratio in terms of the surfaces exposed to gases of combustion in connection with the working volume of the engine. Such high surface to volume ratios tend to cause poor operating efficiency in contributing to poor combustion and high heat rejection to the coolants employed in cooling the various parts. Hard starting and high hydrocarbon emissions are most undesirable results.
The prior art, to partially overcome the handicaps, has proposed two general solutions. According to one solution, ceramic coatings are applied to rotor surfaces in rotary engines between the rotor apices to retard heat transfer. The principal difficulty with this approach is the fact that typical ceramic coatings cannot be made to adhere to the metal of which the rotors are typically formed for prolonged periods of time in the typical working environment. As a consequence, such engines are relatively short lived and thereby unpractical in a commercial sense.
According to the second approach, the typical cavities provided in the rotors to circulate coolant are employed only for the purpose of circulating coolant in the area of the apex seals. Coolant cavities for cooling the rotor surfaces intermediate the apex seals are plugged to form dead air spaces which provide some insulating value to minimize heat rejection. This approach is not structurally sound in that over a prolonged period, stresses within the rotor caused by large temperature differences from one part to another, ultimately cause structure failure.